Advanced methods for continuous insulation condition monitoring on hydrogenerators

Simultaneous stator winding insulation monitoring techniques are compared during on-line, failure-mode testing of a large hydroelectric generator. Three systems that are capable of detecting RF activity on the stator winding are operated during these tests: (1) RFI (radio frequency interference) measurements made at the neutral connection of the generator winding, (2) partial discharge analyzer (PDA) measurements made using capacitive couplers installed at certain locations on the high voltage circuit ring bus, and (3) RF, location-specific measurements made from probes mounted on the generator rotor. Those segments of the failure-mode tests pertaining to the comparative measurements and analysis performed with the three RF monitoring techniques are described. An assessment is made of how each of the three RF monitoring systems can be used to determine the extent to which partial discharge and corona activity are prevalent on the winding, how the location of the RF activity can be used for winding condition diagnosis, and how the extent of the RF activity can be used with other, unrelated generator measurements to determine corrective action, and when needed